This is an application for funds to purchase a JEOL ASID-10 scanning image observation device for a JEOL JEM-1200EX electron microscope. The instrument will be a shared facility to be utilized by a group of investigators who conduct biomedical research at the NYU Medical Center with support from the NIH and other agencies. SEM is a method which has given considerable information on cell surface organization and has great potential for examining membrane surfaces. Recently, progress has been made towards increasing the resolution and versatility of secondary emission SEM. At the level of resolution now attainable (30 A or better) many macromolecular complexes which protrude from membrane surfaces may be visualized directly, especially as it has become possible to greatly reduce the thickness of metal coat applied to the specimen, or to altogether eliminate the requirement for coating by impregnating specimens with heavy metals. In addition, procedures have been introduced which allow a three-dimensional view of intracellular organelles in fractured specimens and new electron dense probes are available which facilitate the detection of specific binding sites on membrane surfaces. Areas of research at the NYU Medical Center which require high resolution SEM facilities are studies such as those carried out within the Dept. of Cell Biology, which aim at determining the distribution of specific markers and labels (such as viruses, antibodies or lectins) on the surface of cells and organelles. In addition, many other projects will greatly benefit from access to a SEM facility of medium to high resolution. These range from basic research work in the Departments of Pharmacology, Microbiology, and Medicine, where a large number of investigators is interested in membrane function, structure and biogenesis, to work with direct clinical relevance, carried out in clinical Departments such as Medicine, Surgery, and Pathology. These investigators utilize most of the biochemical and microscopic methods available for membrane research and several of them are well known electron microscopists. The addition of a high resolution SEM facility will thus benefit a wide spectrum of research at the New York University Medical Center.